Electronic selection of a combustion point or similar point on a wave



5 Sheets-Sheet l Inventors;

John Granville Withers Henry James Hulf Alexander Rubach torneys.

Jan. 19, 1954 J. G. WETHERS ETAL ELECTRONIC SELECTION OF A COMBUSTION POINT OR SIMILAR POINT ON A WAVE Filed June 10, 1950 TRIGGER AMPLIFIER 1:. .im Jun- 2! v 8 8 8 A 3 7 W 7 7 E a m .1 8 1. 7 R E .4 4 n wHs w M R M. m u P M A m. w a T w m9 T 8 6 s l .T n a m a a u Er m MA MW M W s .1. z ex 7 E h EC F me a m x mm m /P BE ORE 7:0.0.

s wywfzwm Jan. 19, 1954 wlTHERS ETAL 2,666,325

ELECTRONIC SELECTION 0F A COMBUSTION POINT OR SIMILAR POINT ON A WAVE Filed June 10, 1950 3 Sheets-Sheet 2 m 7 Fi .3.

M 112 Q 104 b 4 I? 111 105 115 2 119 125 124 F 127 lg Inventor s:

John Granville Withers Henry James Hulf ttog'neys n- 1954 J G. WITHERS ET AL 2 ELECTRONIC SELECTION OF A COMBUSTION I POINT OR SIMILAR POINT ON A WAVE Flled June 10, 1950 3 Sheets-Sheet 3 OUTPUT WAVEFORM 0F INJECTOR PICK-UP WA VEFORM PRODUCED AT THE ANODE 0F VALVE 13.

PRODUCED AT THE CATHODE 0F VflLVEI5 OUTPUT WAVEFORM OF CYLINDER PRESSURE PICK-w? COMBUSTION APPLIED T0 VHLVETIET TIT.

Iggy DIFFERENTIATED WAV EFOR COMBUSTION OUTPUTWAVE- FORM OF REFERENCE PICK-*UPS.

Ni ty 11.

OCCURENCE OF INJECTION OCCURENCE 0F CHANNEL WIGGER PULSE PRESSURE CHANNEL TRIGGER PULSE TIME Inventors:

John Granville Withers Henry James Hulf Alexander Rubach Bywflaflzaarfm orneys Patented Jan. 19, 1954 UNITED STATES PATENT OFFICE.

ELECTRONIGSELECTION OF A COMBUSTION POINT on. SIMILAR POINT ON A WAVE John-Granville Withers and Henry James Hulf, Sunbury onQThames, and Alexander Rubach, Feltham,.England, assignors to Anglo-Iranian Oil, Company Lim d, London. n land. a British joint stockcorporation Application June 10, 1950, Serial No. 167,444 3 Claims. (01. 73-116 This invention-relates to an electronic instrus mentifor'indicating or'r'ecording theperiods be tween signals of two or inore'series of recurring signals. More-particularly-the invention relates toan electronic instrument for comparing the intervals between recurring events in an internal combustion engine. v t

Conventional prior instruments for measuring Iunctions such as the ignition delay of an en ln have necessitated the use of a. cathode ray screen upon which Wasthrown agraphical trace of the required characteristics, such ascyhnder pressure. ona time base.

To obtain the requiredmeasurements"1t was necessaryto employ] a double b m cat eray tube or. when a sin le beam cat d r y tube w employed, t ..makeprovision tor switching over from the graphical. trace to a ibrating t a obtained for example from. a. signal, emitted as thelengine revolved; sivingicrankan le. egree markings. l

In general, such methods necessitated the use of sliding cursorsorother means of re ding the characteristics of one trace whilst h econd trace was referredtoc Such mcthodspweretedious and, ingeneral, had the disadvantago that as traces were obtainedon a. time base their, were dependent uponmaintenance of a constant engine speed. Variations of engine speedlw'ould thusintroduce errors andmeasurements of engine characteristics under conditions of acceleration or deceleration were not possible.

The A S.. T. method ofjCetaneNo... determination involves adjusting .theinjection timing and compression ratio of the (LE. R. diesel ensine, running under standard conditions, so that injection occurs 1 before top dead centre and combustion occurs at top. dead centre. This fix d ignition delay of 13. is obtained for any fuel by a suitable adjustment of compression ratio; and the Octane No. of a samplefuel is determined byinterpolation between the compression ratios found fora fiYeCeta-ne No. bracket of reference fuels.

Injection is detected by arranging that the motion of the spray valve closes a pair of electrical contacts and thereby flashes a gaseous discharge a lamp mounted on the flywheel.

Combustion is detected by a bouncing pin, so adjusted that the contacts just fail to close on compression pressure alone. The increase of pressure due to combustion closes the contacts and flashes a second gaseous discharge lamp mounted on the flywheel. The lamps are so disposed that wheninjectionand combustion occur at the correct times-therespective flashes coinciderwith a cross-mire. 1 o s Some defects of this arrangement are:

(a) The contacts wear and require frequent cleaning and dressing because of contamination and pitting. I

b The con ac spr ng tens req re very acc rate ad u tmen ii sy tem sv to ork at a d. t s ne essit t s f equent re-adiustin nt o mpens e f r wear and emperatu e ffects;-

(c) Since the contacts must be open initially, the indications a e n error by the me taken. tor the cap to lo es s in which an ele tromagnetic pick-up was used to detect, injection have shown that the contact method of indication may lag s much as 2.

(d) T e meth d impos s co si erable ptical strain on an one ator nsased n outi e estin These defects are almost entirely due to the use of electrical contacts, and a method'of presenta-F tion which is not remote indicating.

It is an object of the present invention to provide an improved electronic instrument for indicating or recording the periods between signals of two or more series of recurring signals. It is a further object to provide an electronic instrument forindicating, recording, measuring or comparing the intervals between recurring events in an internal combustion engine. It is a further object to provide an electronic instrument for indicating the ignition delay of an internal combustion engine of the compression-ignition type. Further objects will appear hereinafter.

Thes obj cts e ac omplished y th -p ov sion of an le r ic in trum nt c mprising t o o mor s u ces o re urr n positi e exc rsion e ectrical signa s of sharp na ow pul e elee o switch connected to the said s u ce nd apable f functi nin each of two stable vol a states and adapted to ransmute rom ne state to he other on receipt oI the said clfifitrical signal said switch thereby producin an utgoin i a of n ular Wave for and mete responsive to small current changes, connected to the saideiectroni switch" and actuated by he sa d signal of rectangular wave form. Preferably the meter is a sensitive moving coil galvanometer, such as a milliaarnmeter.

Preferably each. sou ce .Of, ecurrin iwsitive excursi n. el tri al signal. f sh r na rowpnlse omp ses a s e of a gn l ha ingta ecurring positive excursion, thesignal being fed to. the

rid of a thyratron valve operating under cgpditions such that an outgoing signal of the required typeis derived from t e cathode oi he thi/ratr n. the duration of th outs inssienal eing contro ed .bvt e y atro a ode ir ned.anoez Preferably the source of the initial signal having a recurring positive excursion comprises an amplifying valve having a grid circuit with a short time constant, said amplifying valve being coupled to the anode of the thyratron valve whereby the initial pulse of the incoming signal is passed to the thyratron valve and subsequent positive excursions of the same signal are suppressed.

Preferably also, the initial signal is passed through a circuit wherein the wave form of the initial signal is differentiated.

The initial signal will be generated in the manner most suited to the characteristic to be measured. In general, however, it is found convenient to employ an electromagnetic pick-up of variable reluctance type, the outgoing signal being amplified before differentiation as described therefrom to provide a signal of positive going excursions and adapted to differentiate the wave form of the said outgoing signal, an amplifying valve whose input control grid circuit has a short time constant, for receiving the signal of differentiated wave form, and passing the initial pulse of said signal to a thyratron valve, the anode of said thyratron valve being coupled to the said control grid of the prior amplifying valve to suppress subsequent positive excursions of the signal received therein, whereby at the thyratron cathode, there is generated an electrical signal of sharp narrow pulse, constituting the outgoing signal of each of the signal producing units, a switch unit comprising an electronic switch capable of functioning in each of two stable voltage states and adapted to transmute from one state to the other on receipt of signals from one or other of the signal producing units and thereby produce an outgoing signal of rectangular wave form and a meter responsive to small current changes, actuated by the signal of of the fuel injector and an electromagnetic pickup unit actuated by movement of a diaphragm in communication with engine cylinder pressure. Calibration is effected by provision of switching apparatus to switch out the above pick- 11p units and switch into circuit two fixed position pick-up units situated near a rotary component of the engine e. g. the flywheel at a known angle of revolution apart, conveniently 12.5", and which pick-up units emit signals on the passage of a marked graduation on the moving part. The graduation may be a projection, preferably a chisel edge projection on or a groove in the rotary component.

1 The invention is illustrated in a preferred embodiment in Figures 1-11 which relate to an ignition delay meter for use'in conjunction with a four stroke compression-ignition, internal combustion engine.

Figure 1 is a circuit diagram of the electronic instrument.

Figure 2 is a longitudinal cross-section of a pressure sensitive electromagnetic pick-up.

Figure 3 is a longitudinal cross-section of an injector electromagnetic pick-up.

Figure 4 is a longitudinal cross-section of a reference electromagnetic pick-up.

With reference to Figure l the electronic instrument comprises two identical trigger amplifiers, an electronic switch and a metering stage.

An injection responsive pick-up I gives rise to a pulse, of waveform shown in Figure 5 which is passed by switch 2, to the grid of a high gain R. F. pentode valve 3.

After amplification, the signal is resistancecapacity coupled from the anode of the valve 3, to the suppressor grid of amplifying valve 4, whose control grid input circuit has a short time constant, by means of capacity 5, and resistance 12, of such values that the signal is differentiated. Resistances 6, 8, 9 and capacitors I and H) are connected in conventional manner and suitably valued to obtain maximum gain. Capacity II is suitably connected and valued to by-pass any undesirable R. F. signals superimposed. on the input. The amplified signal is coupled from the anode of valve 4, to the grid of ages filled tetrode valve IS. The initial positive part of the signal causes valve H to conduct, discharging capacity H, which then slowly recharges to high potential. The negative voltage wave form produced at the anode of valve l3, illustrated in Figure 6, is coupled back to the control grid of valve 4 in such a manner that all subsequent positive excursions of the signal are suppressed. Resistances I5, [6, I1, [9, 20, 25 and 26 and capacities l4, 2|, 23 and 24 are connected in conventional manner and suitably valued to attain valve operation in the manner described. Capacity 22 is suitably connected and valued to bypass any undesirable R. F. signals superimposed on the input. During the short period during which valve l3 conducts, a positive pulse of very short duration, illustrated in Figure 7 is produced at the cathode of valve I3. The signal is differentiated through coupling of capacity 21, and resistance 28 and is passed to the electronic switch.

A' cylinder pressure-sensitive pick-up 29, having an output proportional to the rate of change of cylinder pressure and of wave form illustrated in Figure 8, is connected by switch 30, to an identical trigger amplifier to that described above, comprising a high gain R. F. pentode valve 3|, valve 32 having a control grid circuit with a short time constant and a gas filled tetrode valve 33. Resistances 34-46 and capacities 4|56 are connected in the manner described above. Figure 9 illustrates the wave-form of the signal after differentiation by the coupling of capacity 50 and resistance 31. The signal further differentiated through the coupling of capacity 56, and resistance 46, is passed to the electronic switch. The potential wave illustrated in Fig. 9, after differentiation by capacity 56 and resistance 46, yields a sharp trigger potential pulse.

The electronic switch consists of four triode valves 51-60 connected so that the voltage relationships may be in one of two states of stable equilibrium.

The arrival of the injection trigger pulse causes the voltage at the anode of valve 59 to assume its upper stable value, and the arrival of the pressure-actuated trigger pulse causes the volta e-at the. anode of valve 58,110 revertto its lower stable value. The transition: from one state-to the other takes about 2 micro-seconds and the'prescnt cir cuit has been tested at switching rates up to 110,000: per second; Resistancesti- -BS and condensers "IO-42 are suitablyconnected and valued to operate the electronic switch and'obtaina wave-dorm as illustrated in Figure 10.

The cyclical repetition ofthis' process results in thegeneration of 'a train -of rectangular waves. themark-space ratio of whichis directly pro portional to the angular interval between injection and ignition; In themetering stage, the signal ofrectangular waveform is resistancecapacity coupled'bycapacityU and resistance andifed to-the-grid of apentode valve-'lfi through resistance I5. The pentode--va1ve'16- ls normally cut-off, conduction occurring only in the interval between injection and ignition. The resulting pulses of anode current are smoothed by the anode capacity 84 to a mean-valueindi'c ated by the moving coil meter 81.

In-orderthat the mean value-indicated by the meter-86 shall be proportional to the mark-space ratio only and'not also to the recurring frequency it is essential that the charge and discharge con stants of theanodecircuit shall be equal. This is accomplished by ensuring that the internal impedance of valve I6 is very much higher than the-anode load resistance II, by the application of negative current feedback.

The" resistances I'L -82v and. capacity 84 are sultablyconnected and yalued to enable the valve 16 -tirolrlerate inthe manner described anda half waverectifier 88 is placed across the indicating meter to protect the meter against overload currents:

"Resistances -M and capaeity- 85 are connected inthe'anode circuit of valvelt in or-der to decouple the h-igh voltage and prevent voltagefluctuations occurring at the anodes of the valves 51-60 of the electronic switch causing spurious operation.

Operating the electronic instrument on receipt J 86 substituted to give a signal at engine-top dead centre. 7

The initial signal wave form; illustrated in Figure 11, is-converted tea-trigger signal by the ignition triggervamplifier.

In order-to calibrate the instrument i to give measurements indegreeszoi crankl angle, the switch .2 has an operating position in which the injection pick-up is cutout otcircuit and a. second reference pick-up 81 is substituted tomgive a signal at,'12.5 beforeengine-otop dead centre.

The switches 2 and 3D areganged to give the following three positions:

(1) Measurement of ignition delay-injection pick-up and ignition pick-up in circuit.

(2) Measurement of injection advanceinjection pick-up and reference pick-up at top dead centre in circuit.

(3) Calibration-top dead centre reference pick-up and 12.5 reference pick up in circuit.

The calibration square wave occurs every revo lution while the delay and injection square waves recur every two revolutions in the case of a -fourstroke engine. Thus the standard calibrating+ meter deflection is double, and in the case consid' ered is equivalent to 259. The meter deflection. is then adjusted to readfull scale: Lay-varying the anode current through valve 'ifiby meansoi vari able resistance 80.

Toensure the stability oimeter calibrations, the high voltage supply and: screengridvoltage supply for valvesfliand .flarestabilised by means of aneon gas stabiliser.

Thefollowing table indicates, with reference to Figure 1; the preferred. componentsior useinan ignition delay meter according :to the invention.

Table Reference no? Figure 1 W Specification "410-; I, Condenser... .do

.Olmicroiarad. 25 microiarads. .(25 Volt. electrolytic) .005 microfarad. .001 microiarad. .Ofldmlcroiarad. .002 microiarad. 50 Micromicrciarads.

.02 microfarad. .5 microiarad.

20 microfarads. 8 mioroiarads.

250 micro amp. moving coll meter.

The ignition (pressure sensitive) pick-up illustrated in Figure 2 is described in detail.

A mildsteel diaphragm I 03, whose thickness is .032 in is located on a seat at thev bottom of the stainless steelbody I01 and. held. there by means of the stainless steel inner body IOZwhich screws into the outerbody andvclamps the diaphragm round its periphery. The 35% cobalt magnet I03 vwith its fStalloy (3% silicon-iron) inserted pole 104 isarranged bymeans of a suitably sized spacer washenlfll such that the pole tip is .002 clear of the diaphragm. The magnet is a sliding. fit inthe innerbody and is heldin position by; the

. clamping nut .109. The terminal takes. the dorm of an amphenol type socket H0. screwed into the top of theinner body above. the. clamping nut. The pick-up 0011.105 of 7.000 turns wound onthe Stalloy pole piece in a clock-wise direction, looking at the end of the pole with the beginning of the winding .soldered'to the pole and the lead at the other end of the winding brought out through a hole in the magnet to the terminal I H). The magnet is magnetised such that the pole end has a north polarity.

The pressure pick-up assembly is screwed into the engine cylinder so that the mild steel diaphragm I08 is subjected to engine cylinder pressure.

Figure 3 illustrates the injector pick-up assembly screwed into the injector nozzle body H9 so that the Stalloy pole I l is positioned inside the injector spring I as illustrated. The lift pressure of the injector spindle H1 is adjusted by means of shims placed between the spring and of the stainless steel body I I. The Stalloy'f pole is inserted into the 35% cobalt steel magnet H2 which, in turn is screwed into the body such that the distance between the end of the pole and the spindle is .060'in. Lock nut H3 clamps the pick-up in position. The amphenol type terminal socket l I 4 is screwed into thetop of the magnet. The pick-up coil of 5,000 turns is wound on the Stalloy pole in a clockwise direction, looking at the end of the pole, with the beginning of the winding connected to the pole and the lead on the other end of the winding brought out through a hole in the magnet to the terminal H4. Brass flange H6 is used to retain the turns of the winding at the pole end, the magnet being-magnetised such that the pole end has a north polarity. Y

With reference to Figure 4, the reference pickup consists of a magnet and pole I22 made in one piece from 35% cobalt steel, with opposite sides of the pole tip I21 tapered to form a chisel edge. The magnet is threaded so that the pick-up can be locked in position and attached to a carrier plate by means of locknut I23. The terminal IZI is of the amphenol type socket screwed into the head of the magnet. The coil of 200 turns is wound on a split brass bobbin I24 in a clockwise direction looking'at the end of the pole. The beginning of the winding is soldered to the pole and the lead at the opposite end of the winding led through a hole in the magnet to the terminal. The-magnet is magnetised such that the pole end has a south polarity.

All pick-up windings described with reference to Figures 2-4 are baked in Bakelite varnish.

We claim:

1. A system for determining the phase between electric waves comprising an electronic switch having two stable switching conditions and having two inputs for operating the switch to change the condition thereof, a pair of cascaded diiferentiating means connected to one input, a pair of cascaded differentiating means connected to the other input, inputs for each of the differentiating means for supplying thewaves thereto, means controlled by the cyclingof said switch for indicating phase, whereby, points of inflection of a potential curve rather than amplitude may be the determinant and wherein each pair of cascaded diiierentiating means includes the following: a vacuum tube amplifyingv stage having the input thereof connected to receive the output of the first of the pair of cascaded differentiating means, an electron discharge device having at least cathode, control grid and anode with the input thereof connected to receive the output of said amplifying stage, said last named electron discharge device having a cathode follower output circuit, said second differentiating means being connected in said cathode follower output circuit, and coupling means connecting the anode of said electron discharge device and an input of the amplifying stage for suppressing additional pulses from said amplifying stage for a period long in comparison to a pulse duration.

2. A system for determining the'phase between electric waves comprising an electronic switch having two stable switching conditions and having two inputs for operating the switch to change the condition thereof, at least one clifferentiating means connected to one input, at least one differentiating means connected to the other input, inputs for each of the diiferentiating means for supplying the waves thereto, means controlled by the cycling of said switch for in dicating waves whereby points of inflection of a. potential curve rather than amplitude may be the determinant and wherein said electronic switch is of the type providing two electron discharge paths with one path being active and the other path being inactive for alternate switch positions and wherein the indicating means includes an electron discharge devicehaving at least cathode, control grid and anode with the input thereof connected to one of the switch discharge paths so that said last-named electron discharge tube may have space current or be cut off-depending upon the condition of the electron switch and whereinsaid last-named electron discharge device has in the anode circuit a meter and high impedance means in series across a condenser, said high impedance means having a substantially higher impedance than the impedance of said last-named electron discharge device when conducting whereby the charging and discharging rates are substantially equal over different switch operating cycles.

3. In a system of the character described, means for producing a trigger pulse comprising a vacuum tube having at least a cathode, two control grids and anode, an input circuit having a short time constant connected to one control grid for'diiferentiating a signal supplied to said one control grid, a grid controlled gas discharge tube, means for coupling the anode of said vacuum tube to the grid of the gas discharge tube, a condenser connected between the anode of said gas discharge tube and the .other' control grid of said vacuum tube, a resistor connected between the other control grid of said vacuum tube and the cathode thereof, said last-named condenser and resistor together providing negative feedback to the vacuumtube and a differ-- entiating circuit in the output of said gas discharge device. I I JOHN GRANVILLE WITHERSF HENRY JAMES HULF. ALEXANDER RUBACHV References Cited in the file of this patent UNITED STATES PATENTS 

